List of possible dwarf planets

The number of dwarf planets in our Solar System is still not known. Scientists think there could be many, but recent studies suggest there might be fewer than expected. The International Astronomical Union (IAU) has officially recognized six dwarf planets: Ceres in the inner Solar System, and five farther out: Pluto, Eris, Haumea, Makemake, and Quaoar.

Only Pluto and Ceres have been proven to be round enough to be dwarf planets, thanks to space missions like New Horizons and Dawn. Eris is thought to be a dwarf planet because it is about the same size as Pluto. Haumea and Makemake are also often called dwarf planets, even though they haven’t been fully confirmed yet.

Other objects like Gonggong, Orcus, and Sedna are sometimes called dwarf planets if they seem solid enough. Scientists are still learning more about these interesting objects in our Solar System, and new discoveries may change what we know about dwarf planets in the future.

Limiting values

Calculation of the diameter of Ixion depends on the albedo (the fraction of light that it reflects). Current estimates are that the albedo is 11%, a bit under the midpoint of the range shown here and corresponding to a diameter of 700 km.

A dwarf planet must be big enough for its gravity to make it round. But it is hard to know if faraway space objects are round. We only have rough guesses about their sizes.

Some scientists think many objects beyond Neptune could be dwarf planets. Others think only a few are big and dense enough to be round. This depends on if they are made of ice or rock, and how tightly they are packed inside. Right now, we know for sure that only a few objects might be dwarf planets.

Brown's categories	Min. ⌀	Number of objects
Nearly certain	> 900 km	10
Highly likely	600–900 km	17 (27 total)
Likely	500–600 km	41 (68 total)
Probably	400–500 km	62 (130 total)
Possibly	200–400 km	611 (741 total)
Source: Mike Brown, as of October 22, 2020

Likeliest dwarf planets

The International Astronomical Union (IAU) has rules for naming objects in space, but these rules don't always tell us if an object is a dwarf planet. Besides Ceres and four large objects beyond Neptune, Quaoar was called a dwarf planet in a report.

Scientists think objects need to be bigger than about 800 kilometers across to be dwarf planets. Some objects, like Charon, a moon of Pluto, might also be dwarf planets.

Largest measured candidates

Many objects in space have been measured and found to be at least 600 kilometers wide. These include moons like Charon and Dysnomia, which are large enough to possibly be dwarf planets themselves. Ceres, already accepted as a dwarf planet, is also listed for comparison.

Brightest unmeasured candidates

For objects that haven't been measured yet, scientists estimate their sizes based on how bright they appear. These estimates depend on guesses about how reflective the objects are. Some of these objects might be large enough to be dwarf planets, but we need more data to know for sure.

Possible dwarf planets with measured sizes or masses
(satellites Triton, Charon, Dysnomia included for comparison)
Designation	H	Geometric albedo	Diameter (km)	Method	Mass (10¹⁸ kg)	Density (g/cm³)	moons	Category	ID'd as a dwarf
Designation	H	Geometric albedo	Diameter (km)	Method	Mass (10¹⁸ kg)	Density (g/cm³)	moons	Category	Emery et al.	Grundy et al.
Neptune I Triton	−1.2	60% to 95%	2707±2	direct	21389±28	2.061		satellite of Neptune
134340 Pluto	−0.45	49% to 66%	2377±3	direct	13025±6	1.854±0.006	5	2:3 resonant
136199 Eris	−1.21	96%	2326±12	occultation	16466±85	2.43±0.05	1	SDO
136108 Haumea	0.21	49%	1559	occultation	3986±43	≈ 2.018	2	classical
136472 Makemake	−0.21	83%	1430±14	occultation	2690±200	1.76±0.17	1	classical
225088 Gonggong	1.86	14%	1230±50	thermal	1750±70	1.74±0.16	1	3:10 resonant
134340 Pluto I Charon	1	20% to 50%	1212±1	direct	1586±15	1.702±0.017		satellite of Pluto
50000 Quaoar	2.42	11%	1098±2	occultation	1212±5	1.75±0.013	1 (2?)	classical
1 Ceres	3.33	9%	939.4±0.2	direct	938.35±0.01	2.16±0.01	0	asteroid belt
90482 Orcus	2.18	23% ± 2%	910+50 −40	thermal	548±10	1.4±0.2	1	2:3 resonant
90377 Sedna	1.52	41%	906+314 −258 (occult. chord 1025±135)	thermal			0	detached
120347 Salacia	4.26	5%	838±44	thermal	492±7	1.50±0.12	1	classical
307261 Máni	3.62	10%	796±24	occultation			0	classical
208996 Achlys	3.77	11%	772±12	occultation		0.87 (assuming HE)	1	2:3 resonant
55565 Aya	3.47	11%	768+39 −38	thermal			0	classical
174567 Varda	3.46	11%	749±18	occultation	245±6	1.78±0.06? or 1.23±0.04?	1	classical
532037 Chiminigagua	3.12	18%	742+78 −83	thermal	§		1	SDO
28978 Ixion	3.85	11%	696.78+10.75 −8.87	occultation			0	2:3 resonant
90568 Goibniu	3.99	8%	680±34	thermal		1.14–1.49 (assuming a Jacobi ellipsoid)	0	classical
145452 Ritona	3.69	11%	679+55 −73	thermal			0	classical
55637 Uni	3.85	12%	659±38	thermal	125±3	0.82±0.11	1	classical
20000 Varuna	3.79	12%	654+154 −102	thermal		0.992+0.086 −0.015 (assuming HE)	0 (1?)	classical
145451 Rumina	4.63	11%	644	occultation			0	SDO
229762 Gǃkúnǁʼhòmdímà	3.5	14%	642±28	occultation	136±3	1.04±0.17	1	SDO
2014 UZ224 ("DeeDee")	3.48	14%	635+65 −72	thermal	§		0	SDO
136199 Eris I Dysnomia	5.6	5±1%	615+60 −50	thermal		0.7±0.5		satellite of Eris
(303775) 2005 QU182	3.75	13%	584+155 −144	thermal	§		0	SDO
78799 Xewioso	4.86	4%	565+71 −73	thermal			0	classical

Sizes in km calculated from assumed albedos
for brightest objects without measured size or mass
H	Objects with this magnitude (H)	Diameter of object at the bright end of this range, for an assumed albedo (p) of:
H	Objects with this magnitude (H)	4%	6%	8%	10%	12%	14%	16%	18%	20%
3.60–3.69	^§2021 DR15 (H = 3.61 ± 0.15)	1,270	1,030	900	800	730	680	630	600	570
3.70–3.79	^§2017 OF201 (H = 3.72 ± 0.09)	1,210	990	860	770	700	650	610	570	540
3.80–3.89	^§2010 RF₄₃, 2015 RR₂₄₅, ^§2010 JO₁₇₉, ^§2014 EZ₅₁	1,160	940	820	730	670	620	580	540	520
3.90–3.99	^§2018 VG18 ("Farout"; H = 3.94 ± 0.52)	1,100	900	780	700	640	590	550	520	490
4.00–4.09	2010 KZ39, ^§2012 VP113 ("Biden"), ^§2021 LL37 (H = 4.09 ± 0.31)	1,050	860	750	670	610	560	530	500	470
4.10–4.19	^§2015 KH₁₆₂, 2020 MK53 (lost; H = 4.12 ± 0.35)	1,010	820	710	640	580	540	500	470	450
4.20–4.29	2008 ST₂₉₁, 2018 AG37 ("FarFarOut"; H = 4.22 ± 0.1), ^§2013 FZ₂₇, 2010 RE₆₄	960	780	680	610	560	510	480	450	430
4.30–4.39	^§2014 WK₅₀₉, ^§2015 BP₅₁₉ ("Caju"), ^§2017 OF₆₉, ^§2014 AN₅₅, ^§2017 FO161, 2016 NY210 (H = 4.38 ± 0.74)	920	750	650	580	530	490	460	430	410
4.40–4.49	^§2014 WP₅₀₉, ^§2013 XC₂₆, 2007 JJ₄₃, 2014 YA50	880	720	620	550	510	470	440	410	390
4.50–4.59	^§2010 FX86, 2010 OO₁₂₇	840	680	590	530	480	450	420	390	370
4.60–4.69	2007 XV₅₀, 2006 QH181, 2025 MZ348, 2014 OE₃₉₄, 2002 WC₁₉, ^§2014 HA₂₀₀, ^§2014 US277, ^§2010 DN₉₃	800	650	570	510	460	430	400	380	360
4.70–4.79	^§2014 BV₆₄, 2014 FC69, ^§2015 BZ₅₁₈, 2014 FC₇₂, 2020 FY30 (H = 4.71 ± 0.16), ^§2014 US₂₂₄, ^§2015 AM₂₈₁, 2010 VK₂₀₁, ^§2014 TZ₈₅	760	620	540	480	440	410	380	360	340
4.80–4.89	^§2011 WJ₁₅₇, ^§2007 JH₄₃, ^§2008 OG₁₉, 2014 FT₇₁	730	600	520	460	420	390	360	340	330
4.90–4.99	2011 HP83, 2013 FS28, ^§2014 UM₃₃, ^§2014 VU₃₇, 2013 AT₁₈₃, 2014 BZ₅₇, ^§2014 JR₈₀, ^§2003 UA₄₁₄, ^§2011 OA₆₀, ^§2013 SF106 (H = 4.96 ± 0.27)	700	570	490	440	400	370	350	330	310

Limiting values

Likeliest dwarf planets

Largest measured candidates

Brightest unmeasured candidates

Images

Related articles